Question 14245
a-5=-3;  a= 2

Just simplify a-5=-3
a-5=-3
a-5+5=-3+5
a+0=5-3
a=2

and

a-9+6a;  7a-9
Just simplify a-9+6a
a-9+6a
=a+6a-9
=(1+6)a-9
=7a-9

OK